Sliding potentiometer with a slider movable by a roller gear

ABSTRACT

A sliding potentiometer including a slider movable by a roller gear, which slider electrically connects a resistance strip and a contact strip with each other, the roller gear being drivingly connected to a rack arranged in parallel to the resistance strip by means of a pinion coupled to the roller gear. The potentiometer is provided with means for uncoupling the drive connection of the roller gear in the thermal areas of the roller gear&#39;&#39;s path of motion and means for limiting the translational movement of the roller gear in the terminal areas of the roller gear&#39;&#39;s path of movement.

United States Patent [in v in] I 3,708,777

volkheimer 1 Jan. 2, 1973 s41 SLIDING POTENTIOMETERv WITH A 3,465,277 9/1969 Bang .sssnsa SLIDER MOVABLE BY A ROLLER 3,582,860 6/1971 Milovac ..338/l83 GEAR E v Primary xaminerLewis H. Myers [75] Inventor. lztrlzgn Volkheimer, Trossingen, Assistant Examiner D A Tone y Attorney-Craig and Antonelli [73] Assignee: Firma Hopt Electronic GmbH, Rottweil, Germany [5 7] ABSTRACT Filedi y 1971 A sliding potentiometer including a slider movable by [211 App. NOJ 147 893 a roller gear, which slider electrically connects a resistance strip and a contact strip with each other the roller gear being drivingly connected to a rack ar- UsS. ranged in parallel to the resistance means of a [5 Cl. ..H01C to roller gear is v [58] Fleld of Search ..338/ 183, 176 provided i h means for uncoupling the drive connec tion of the roller gear in the thermal areas of the roller [56] References Cned gears path of motion and means for limiting the trans- UNITED STATES PATENTS lational movement of the roller gear in the terminal areas of the roller gears path of movement. 3,096,500 7/1963 Daily et al. ..338/183 3,431,530 3/1969 Bang ..338/183 8 Claims, 3 Drawing Figures h I 3 i 2 7 21 9 12 5 I I i i I D L O o O o PATENTEBJAN 2191s 3,708,777

INVENTOR I LOTHAR VOLKHEIMER BY cw flmxomw 9 mm ATTORNEYS SLIDING POTENTIOMETER WITH A SLIDER MOVABLE BY A ROLLER GEAR The invention deals with a sliding potentiometer comprising a slider movable by a roller gear, in which the slider electrically connects a resistance strip and a contact strip with each other, the roller gear being provided with a pinion which rolls on a rack which is parallel to the resistance strip.

In a known roller-gear actuated sliding potentiometer of this kind, the slider is accommodated in the hub of the roller gear and consists of a compression spring, which at both ends presses the contact rivets which stand out of the frontal surfaces of the roller gear hub outwards, where they come to bear against the resistance strip or the contact strip, as the case may be.

A sliding potentiometer with roller gear actuation has also become known, in which the roller gear hub engages the recesses of a carriage which is slidably conducted along the resistance strip and translationally carries the carriage, which supports the slider, along in the rolling off movement. In the two aforementioned known constructions of sliding otentiometers, the movement of the roller gear in the terminal areas of the resistance strip or of the contact strip, as the case may be, is limited by a stop on which the roller gear or the 'carriage runs up. In this connection, it is disadvantageous that this running up is effected in a relatively hard manner, which affects the service life of the sliding potentiometer unfavorably. This hard stop is, however, especially disadvantageous when the roller gear of the sliding potentiometer is in its terminal position and a person using it does not know that the roller gear is already in terminal position and tries to still move the roller gear further. Without this person having to expend any very great force, this can quickly result in the sliding potentiometer being damaged and becoming unserviceable, because the gearing of rack and pinion is designed with a relatively small module on account of the small construction size and because rack and pinion are extruded out of plastic in the interest of cheapness of manufacture and consequently only exhibit a very limited strength. An additional factor is still that there is a considerable gear ratio from the circumference of the roller gear to the pitch circle of the pinion, that is to say the operating force acting upon the circumference of the roller gear is converted into its multiple value. A careless displacement of the roller gear can in view of the above circumstances result in the breaking off of teeth from pinion or rack, which means that the potentiometer becomes useless.

The task of the present invention is to create a sliding potentiometer which is roller gear actuated and is protected against damage by careless moving of the roller gear into a terminal position.

The task is solved in accordance with the invention by providing a coupling which uncouples in the terminal areas of the roller gears path of motion and which terminates the translation movement independently of the rotation of the roller gear.

The special advantage of the invention resides in the fact that a roller gear actuated sliding potentiometer cannot be damaged and destroyed by an over turning of the roller gear in its end position any more. Even in those cases in which the roller gear is already at the end of its path of motion and the person who uses is not perhaps aware of this fact and tries to still turn the roller gear, no damage can occur by breaking off of teeth from the pinion and the rack, since the transmission of power from the roller gear circumference to the rack via the pinion is interrupted.

The coupling can thereby be designed for instance as a slipping clutch, which is intercalated between pinion and roller gear. Or the roller gear can be provided with an outer ring, which can be turned around with regard to the inner part of the roller gear which supports the pinion when a certain torque is exceeded. In a preferred specific embodiment, on the other hand, the rack is shorter than the area of travel of the rolling gear axis so that the pinion comes out of gear with rack at the end of the area of travel. In this amazingly simple manner, the uncoupling is secured in the desired area without a special outlay of technical manufacturing or assembling means being required in order to do so. When movement is reversed, the pinion engages the rack again, since the sense of rotation of roller gear and pinion is the same and the actuating force exercised upon the roller gear acts in the desired direction.

In one specific embodiment of a sliding potentiometer, in which the roller gear moves a carriage supporting the slider in a straight guide parallel to the resistance strip and the carriage exhibits recesses extending transversely to the path of motion into which the roller gear hub engages, provision is made for the carriage to be provided with flexible tabs projecting in its directions of travel which come resiliently to bear against an abutment surface at the terminal points of the carriages path of, travel. In this form of construction of the invention, the tabs of the carriage which come to bear resiliently against a solid surface ensure that the pinion invariably comes into gear again in the terminal area of the rack, regardless of how the direction of the operating force acts upon the roller gear. In addition, the flexible tabs cause a smooth braking of the roller gear and of the carriage in the terminal area of their path of motion, without the function of the coupling being impaired in any manner as a result.

In one specific embodiment of the invention, in which the sliding potentiometer comprises a carriage which has an U-shaped cross-section perpendicular to the direction of movement, the yoke of the U-shaped carriage is prolonged in the direction of the carriages movement and constitutes a part of the straight guide of the carriage. The sliding potentiometer thereby exhibits at least one groove extending in the direction of the carriages movement, into which lateral projections of the yoke prolongation engage. An advantage of this form of construction of the carriage is that the base of the straight guide is relatively long so that no tilting and consequent jamming of the carriage can occur, which would result in an uneven movement of the roller gear. In preferred forms of construction of the invention, the carriage and slider are manufactured in one piece. They are preferably punched out and bent out of a corresponding sheet metal in one operation.

In a specially preferred form of construction of the invention, the carriage is designed as a brake acting upon the roller gear and impeding its rotation. As a result a reliable holding of the potentiometers adjustment is secured, since the braking of the roller gear by the carriage which is protected against turning on account of its straight guide reliably prevents any shifting 3 of the slider. The braking can thereby be effected for instance by flexible tabs of the carriage which lie against the periphery of the roller gear or by flexible shanks of the carriage which lie against the sides of the roller gear.

Further details and forms can be taken from the following description of a specific embodiment of the invention represented in the drawing.

FIG. 1 shows a cross-section through a roller gear actuated sliding potentiometer designed in accordance with the invention, along the line l--l,

FIG. 2 shows a topview of the sliding potentiometer in the direction of arrow 11 of FIG. 1, when the upper housing half has been removed, and

FIG. 3 shows the schematic drawing of a carriage spread out in one plane, as it appears as a stamped metal part before being bent into its final form.

The sliding potentiometer of the invention is surrounded on all sides by a housing which consists of two housing halves 1 and 2, which are assembled and which leave a slot-shaped opening on one longitudinal narrow side, through which a roller gear 3 projects outwardly somewhat. On the opposite longitudinal narrow side, connecting lugs 4 are conducted outwards, which are intended to be soldered into printed circuits and which are electrically connected with the ends of a resistance strip 5 and with a contact strip 6. The resistance strip 5 and the contact strip 6 extend in the longitudinal direction of the housing in the wall area of the two housing halves l and 2, in the vicinity of the longitudinal narrow side on which the connecting lugs 4 emerge. The resistance strip 5 and the contact strip 6 have the shape of an elongated strip and are fastened to the housing half 1 or to the housing half 2, as the case may be, in known fashion, thus, they are for instance inserted, fitted in, cemented or riveted. The housing half 1 is provided with a narrow groove 7 extending in its longitudinal direction, the width of which is slightly bigger than the diameter of a hub pin 8 of the roller gear 3. The hub pins 8 are joined to a hub shoulder 9 which has a bigger diameter and which is continued into the side surface 10 of the roller gear 3. On its other side, the roller gear 3 exhibits an identical side surface 10, which is continued in an identical hub shoulder 9. This other hub shoulder 9 is joined in axial direction to a pinion 11, which engages in a rack 12, which is molded into the housing half 2 and which extends in the longitudinal direction of housing half 2. The pinion thereby engages the rack 12 from the side facing the opening for the roller gear 3. When the peripheral section of the roller gear 3 which protrudes outside the housing is rotated, the pinion 11 rolls off the rack 12 and the roller gear moves along the longitudinal direction of rack 12 and groove 7, which provides an additional guide.

In their lateral wall, in the vicinity of their narrow longitudinal side facing away from the opening for the roller gear 3, the housing halves 1 and 2 each exhibit a groove 13, which extends in the longitudinal direction of the housing halves 1 and 2.

The electrical connection of the resistance strip 5 with the contact strip 6 is effected via a slider, which is designed in one piece with a carriage 14. The carriage 14, which is symmetrical to the longitudinal median plane of the sliding potentiometer, supports two flexible arms 15 and 16, on the free ends of which contact I rivets 17 and 18 are affixed, which bear against the resistance strip or the contact strip, as the case may be, and which provide their electrical connection with each other.

As seen in the longitudinal direction of the grooves 13, the carriage has an U-shaped form, whose yoke 19 is provided with a reinforcing longitudinal corrugation 20. From the yoke 19, which is aligned roughly parallel to the longitudinal narrow surface of the housing bearing the connecting lugs 4, shanks 21 issue, which lie resiliently against the side surfaces 10 of the roller gear 3. At their free ends, the shanks 21 have semicircular recesses 22, the diameter of which is roughly the same as the diameter of the hub shoulders 9 of the roller gear 3 and in which the hub shoulders 9 of the roller gear 3 engage. The shanks 21 are provided with depressions 23 facing each other, which lie against the side surfaces 10 of the roller gear 3 and which effect their braking against rotation. The flexible arms 15 and 16 are stamped out of the surface of the shanks 21. The root area of the flexible arms 15 and 16 issue from the yoke 19 of the carriage 14. The yoke 19 is prolonged on both sides in the direction of the carriages movement. These prolongations 24, into the area of which the longitudinal corrugation 20 still extends, exhibit laterally projecting tabs 26 provided with lateral corrugations 25 which, together with the prolongations 24, lie in the plane of the yoke. The tabs 26 extend into the grooves 13 of the two housing halves l and 2. Together with the grooves, they provide a straight guide with a relatively big base for the carriage 14, as a result of which a tilting and turning over of the carriage is prevented. The prolongation 24 is joined to tabs 27 extending in the longitudinal direction of the prolongation 24, which are bent out of the yoke plane surface about a folded edge 28. In their end area, the tabs 27 are again bent around an edge 29. Together with a stop surface 30, the edges 29 of the flexible tabs form a resilient stop; the stop surfaces 30 are molded on to the housing halves 1 and/or 2.

If the roller gear 3 is rotated from outside, then, as a result of the pinion 11 rolling off the rack 12, it moves in the direction of the longitudinal sense of the resistance strip 5 and of the contact strip 6. Since the hub shoulders 9 of the roller gear 3 engage the recesses 22 of the shanks 21 of the carriage 14, the longitudinal motion is transmitted to the carriage 14, which is prevented from any tilting and turning over by the tabs 26 which are conducted in the grooves 13. If the rotation of the roller gear is brought to an end, the position reached by the carriage, slider and roller gear is retained, since the shanks 21 of the carriage l4 lie against the side surfaces 10 of the roller gear 3 and prevent its further rotation, which might for instance be caused by vibrations or suchlike. A reliable holding of the adjusted position and consequently a reliable holding of the desired resistance value of the potentiometer is secured as a result.

The rack 12 is provided symmetrically to the length of the resistance strip 5 or of the contact strip 6, as the case may be. The length of the rack 12 is thereby so limited that the pinion 11 comes out of gear at the end of the rack 12, before the roller gear 3 has reached the mechanically limit end of its path of motion. Just before the pinion 11 comes out of gear with the rack 12, the edge 29 of the flexible tab 27 comes to lie against the stop surface 30. As a result of this, a smooth braking of the carriage and of the roller gear is secured and, in addition, the elastic force of the tab 27 causes the pinion l 1 to engage the rack 12 again.

It is understood that the invention is not limited to the form of construction which has been described; rather are modifications of it possible without departing from the spirit of the invention. In particular, the shape of the carriage can be so changed that the braking of the roller gear is effected on its peripheral area.

I claim:

1. Sliding potentiometer comprising a slider movable by a roller gear, the slider electrically connecting a resistance strip and a contact strip with each other, drive means for coupling the roller gear to a rack arranged in parallel to the resistance strip, the drive means including a pinion provided on the roller gear for rolling on the rack, and means for uncoupling the drive means in the terminal areas of the roller gears path of motion and for terminating the translational movement of the roller gear independently of the rotational movement thereof.

2. The sliding potentiometer in accordance with claim 1, characterized in that the rack (12) is shorter than the range of motion of the roller gear axis in such a manner that the pinion (1 1) comes out of gear with the rack (12) at the end of the range of movement of the roller gear (3).

3. The sliding potentiometer in accordance with claim 1, in which the roller gear moves a slider-supporting carriage in a straight guide parallel to the resistance strip, characterized in that the carriage (14) is provided with flexible tabs (27) which project in its directions of movement and which come to lie resiliently against an abutment surface (30) at the terminal points of the carriages path of motion.

4. The sliding potentiometer in accordance with claim 3, characterized in that the flexible tabs (27) of the carriage (14) begin to lie against the abutment surface (30) while the pinion (11) is in engagement with the rack (12).

5. The sliding potentiometer in accordance with claim 3, comprising a carriage with a cross-section which is U-shaped perpendicularly to the direction of movement, characterized by the yoke (19) of the U- shaped carriage (14) being prolonged in the direction of the carriages movement and constituting a part of the straight guide (13, 26) of the carriage (l4).

6. The sliding potentiometer in accordance with claim 5, characterized in that it exhibits at least one groove (13) extending in the direction of movement of the carriage (14) into which lateral tabs (26) of the yoke prolongation (24) engage.

7. The sliding potentiometer in accordance with claim 3, characterized by the carriage (l4) and the slider (l5, 16, 17, 18) being manufactured in one piece.

8. The sliding potentiometer in accordance with claim 3, characterized in that the carriage (14) includes means for acting upon the roller gear for braking and impeding the rotation thereof. 

1. Sliding potentiometer comprising a slider movable by a roller gear, the slider electrically connecting a resistance strip and a contact strip with each other, drive means for coupling the roller gear to a rack arranged in parallel to the resistance strip, the drive means including a pinion provided on the roller gear for rolling on the rack, and means for uncoupling the drive means in the terminal areas oF the roller gear''s path of motion and for terminating the translational movement of the roller gear independently of the rotational movement thereof.
 2. The sliding potentiometer in accordance with claim 1, characterized in that the rack (12) is shorter than the range of motion of the roller gear axis in such a manner that the pinion (11) comes out of gear with the rack (12) at the end of the range of movement of the roller gear (3).
 3. The sliding potentiometer in accordance with claim 1, in which the roller gear moves a slider-supporting carriage in a straight guide parallel to the resistance strip, characterized in that the carriage (14) is provided with flexible tabs (27) which project in its directions of movement and which come to lie resiliently against an abutment surface (30) at the terminal points of the carriage''s path of motion.
 4. The sliding potentiometer in accordance with claim 3, characterized in that the flexible tabs (27) of the carriage (14) begin to lie against the abutment surface (30) while the pinion (11) is in engagement with the rack (12).
 5. The sliding potentiometer in accordance with claim 3, comprising a carriage with a cross-section which is U-shaped perpendicularly to the direction of movement, characterized by the yoke (19) of the U-shaped carriage (14) being prolonged in the direction of the carriage'' s movement and constituting a part of the straight guide (13, 26) of the carriage (14).
 6. The sliding potentiometer in accordance with claim 5, characterized in that it exhibits at least one groove (13) extending in the direction of movement of the carriage (14) into which lateral tabs (26) of the yoke prolongation (24) engage.
 7. The sliding potentiometer in accordance with claim 3, characterized by the carriage (14) and the slider (15, 16, 17, 18) being manufactured in one piece.
 8. The sliding potentiometer in accordance with claim 3, characterized in that the carriage (14) includes means for acting upon the roller gear for braking and impeding the rotation thereof. 